Planetary gear train of automatic transmission for vehicle

ABSTRACT

A planetary gear train of an automatic transmission for a vehicle may include: an input shaft receiving torque of an engine; an output shaft outputting changed torque; a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element; a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element; a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element; and a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and the benefit of KoreanPatent Application No. 10-2015-0087713 filed on Jun. 19, 2015, theentire contents of which is incorporated herein for all purposes by thisreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic transmission for avehicle. More particularly, the present invention relates to a planetarygear train of an automatic transmission for a vehicle that improvespower delivery performance and reduces fuel consumption by achieving tenforward speed stages and widening gear ratio span using a minimum numberof constituent elements and securing linearity of step ratios.

Description of Related Art

In recent years, a rise in oil price causes dashing into unlimitedcompetition for enhancing fuel efficiency.

As a result, researches into reduction of a weight and the enhancementof the fuel efficiency through down sizing are conducted in the case ofan engine and researches for simultaneously securing operability andfuel efficiency competitiveness through multiple speed stages areconducted in the case of an automatic transmission.

However, in the automatic transmission, as the number of speed stagesincrease, the number of internal components increase, and as a result,mountability, cost, weight, transmission efficiency, and the like maystill deteriorate.

Accordingly, development of a planetary gear train which may bring aboutmaximum efficiency with a small number of components may be important inorder to increase a fuel efficiency enhancement effect through themultistages.

In this aspect, in recent years, 8-speed automatic transmissions tend tobe implemented and the research and development of a planetary geartrain capable of implementing more speed stages has also been activelyconducted.

However, since a conventional 8-speed automatic transmission has gearratio span of 6.5-7.5, improvement of fuel economy may not be great.

In addition, if 8-speed automatic transmission has gear ratio spanlarger than 9.0, it is hard to secure linearity of step ratios.Therefore, driving efficiency of an engine and drivability of a vehiclemay be deteriorated, and thus, development of high efficiency automatictransmissions which achieve at least nine forward speed stages isnecessary.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing aplanetary gear train of an automatic transmission for a vehicle havingadvantages of improving power delivery performance and fuel economy byachieving ten forward speed stages and two reverse speed stages andwidening gear ratio span and of securing linearity of step ratios.

A planetary gear train of an automatic transmission for a vehicleaccording to an exemplary embodiment of the present invention mayinclude: an input shaft receiving torque of an engine; an output shaftoutputting changed torque; a first planetary gear set including first,second, and third rotation elements; a second planetary gear setincluding fourth, fifth, and sixth rotation elements; a third planetarygear set including seventh, eighth, and ninth rotation elements; and afourth planetary gear set including tenth, eleventh, and twelfthrotation elements, wherein the input shaft is directly connected to thefourth rotation element and is selectively connected to the eleventhrotation element, the output shaft is directly connected to the twelfthrotation element, the twelfth rotation element is directly connected tothe eighth rotation element, the third rotation element is directlyconnected to the seventh and tenth rotation elements, the secondrotation element is directly connected to the sixth rotation element,the first rotation element is selectively connected to the eighthrotation element, the fourth rotation element is selectively connectedto the fifth rotation element, the third rotation element is selectivelyconnected to the fifth rotation element, the fifth rotation element isselectively connected to the transmission housing, the first rotationelement is selectively connected to the transmission housing, and theninth rotation element is selectively connected to the transmissionhousing.

The first, second, and third rotation elements of the first planetarygear set may be a first sun gear, a first planet carrier, and a firstring gear, the fourth, fifth, and sixth rotation elements of the secondplanetary gear set may be a second sun gear, a second planet carrier,and a second ring gear, the seventh, eighth, and ninth rotation elementsof the third planetary gear set may be a third sun gear, a third planetcarrier, and a third ring gear, and the tenth, eleventh, and twelfthrotation elements of the fourth planetary gear set may be a fourth sungear, a fourth planet carrier, and a fourth ring gear.

Each of the first, second, third, and fourth planetary gear sets may bea single pinion planetary gear set.

The planetary gear train may further include: a first clutch selectivelyconnecting the first rotation element to the eighth rotation element; asecond clutch selectively connecting the fourth rotation element to thefifth rotation element; a third clutch selectively connecting the inputshaft to the eleventh rotation element; a fourth clutch selectivelyconnecting the third rotation element to the fifth rotation element; afirst brake selectively connecting the fifth rotation element to thetransmission housing; a second brake selectively connecting the firstrotation element to the transmission housing; and a third brakeselectively connecting the ninth rotation element to the transmissionhousing.

A planetary gear train of an automatic transmission for a vehicleaccording to another exemplary embodiment of the present invention mayinclude: an input shaft receiving torque of an engine; an output shaftoutputting changed torque; a first planetary gear set including first,second, and third rotation elements; a second planetary gear setincluding fourth, fifth, and sixth rotation elements; a third planetarygear set including seventh, eighth, and ninth rotation elements; and afourth planetary gear set including tenth, eleventh, and twelfthrotation elements, wherein the input shaft is directly connected to thefourth rotation element and is selectively connected to the eleventhrotation element, the output shaft is directly connected to the twelfthrotation element, the twelfth rotation element is directly connected tothe eighth rotation element, the third rotation element is directlyconnected to the seventh and tenth rotation elements, the secondrotation element is directly connected to the sixth rotation element,the first rotation element is selectively connected to the eighthrotation element, the fifth rotation element is selectively connected tothe sixth rotation element, the third rotation element is selectivelyconnected to the fifth rotation element, the fifth rotation element isselectively connected to the transmission housing, the first rotationelement is selectively connected to the transmission housing, and theninth rotation element is selectively connected to the transmissionhousing.

The first, second, and third rotation elements of the first planetarygear set may be a first sun gear, a first planet carrier, and a firstring gear, the fourth, fifth, and sixth rotation elements of the secondplanetary gear set may be a second sun gear, a second planet carrier,and a second ring gear, the seventh, eighth, and ninth rotation elementsof the third planetary gear set may be a third sun gear, a third planetcarrier, and a third ring gear, and the tenth, eleventh, and twelfthrotation elements of the fourth planetary gear set may be a fourth sungear, a fourth planet carrier, and a fourth ring gear.

Each of the first, second, third, and fourth planetary gear sets may bea single pinion planetary gear set.

The planetary gear train may further include: a first clutch selectivelyconnecting the first rotation element to the eighth rotation element; asecond clutch selectively connecting the fifth rotation element to thesixth rotation element; a third clutch selectively connecting the inputshaft to the eleventh rotation element; a fourth clutch selectivelyconnecting the third rotation element to the fifth rotation element; afirst brake selectively connecting the fifth rotation element to thetransmission housing; a second brake selectively connecting the firstrotation element to the transmission housing; and a third brakeselectively connecting the ninth rotation element to the transmissionhousing.

A planetary gear train of an automatic transmission for a vehicleaccording to another exemplary embodiment of the present invention mayinclude: an input shaft receiving torque of an engine; an output shaftoutputting changed torque; a first planetary gear set including first,second, and third rotation elements; a second planetary gear setincluding fourth, fifth, and sixth rotation elements; a third planetarygear set including seventh, eighth, and ninth rotation elements; afourth planetary gear set including tenth, eleventh, and twelfthrotation elements; a first rotation shaft connected to the firstrotation element and selectively connected to a transmission housing; asecond rotation shaft connecting the second rotation element to thesixth rotation element; a third rotation shaft connecting the thirdrotation element to the seventh and tenth rotation elements; a fourthrotation shaft connected to the fourth rotation element and directlyconnected to the input shaft; a fifth rotation shaft connected to thefifth rotation element, selectively connected to the transmissionhousing, and selectively connected to the third rotation shaft; a sixthrotation shaft connecting the eighth rotation element to the twelfthrotation element, selectively connected to the first rotation shaft, anddirectly connected to the output shaft; a seventh rotation shaftconnected to the ninth rotation element and selectively connected to thetransmission housing; and an eighth rotation shaft connected to theeleventh rotation element and selectively connected to the input shaft,wherein the second planetary gear set is selectively locked-up byselectively connecting two rotation elements among three rotationelements of the second planetary gear set.

The first planetary gear set may be a single pinion planetary gear setand may include a first sun gear as the first rotation element, a firstplanet carrier as the second rotation element, and a first ring gear asthe third rotation element. The second planetary gear set may be asingle pinion planetary gear set and may include a second sun gear asthe fourth rotation element, a second planet carrier as the fifthrotation element, and a second ring gear as the sixth rotation element.The third planetary gear set may be a single pinion planetary gear setand may include a third sun gear as the seventh rotation element, athird planet carrier as the eighth rotation element, and a third ringgear as the ninth rotation element. The fourth planetary gear set may bea single pinion planetary gear set and may include a fourth sun gear asthe tenth rotation element, a fourth planet carrier as the eleventhrotation element, and a fourth ring gear as the twelfth rotationelement.

In one aspect, the second planetary gear set may be locked-up byconnection of the fourth rotation element and the fifth rotationelement.

The planetary gear train may further include: a first clutch selectivelyconnecting the first rotation shaft to the sixth rotation shaft; asecond clutch selectively connecting the fourth rotation shaft to thefifth rotation shaft; a third clutch selectively connecting the inputshaft to the eighth rotation shaft; a fourth clutch selectivelyconnecting the third rotation shaft to the fifth rotation shaft; a firstbrake selectively connecting the fifth rotation shaft to thetransmission housing; a second brake selectively connecting the firstrotation shaft to the transmission housing; and a third brakeselectively connecting the seventh rotation shaft to the transmissionhousing.

In another aspect, the second planetary gear set may be locked-up byconnection of the fifth rotation element and the sixth rotation element.

The planetary gear train may further include: a first clutch selectivelyconnecting the first rotation shaft to the sixth rotation shaft; asecond clutch selectively connecting the second rotation shaft to thefifth rotation shaft; a third clutch selectively connecting the inputshaft to the eighth rotation shaft; a fourth clutch selectivelyconnecting the third rotation shaft to the fifth rotation shaft; a firstbrake selectively connecting the fifth rotation shaft to thetransmission housing; a second brake selectively connecting the firstrotation shaft to the transmission housing; and a third brakeselectively connecting the seventh rotation shaft to the transmissionhousing.

Exemplary embodiments of the present invention may achieve ten forwardspeed stages and two reverse speed stages by combining four planetarygear sets with seven control elements.

In addition, since gear ratio span greater than 9.0 is secured, drivingefficiency of the engine may be maximized.

In addition, since linearity of step ratios is secured, drivability suchas acceleration before and after shift, rhythmical engine speed, and soon may be improved.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a planetary gear train according to thefirst exemplary embodiment of the present invention.

FIG. 2 is a schematic diagram of a planetary gear train according to thesecond exemplary embodiment of the present invention.

FIG. 3 is an operation chart of control elements at each speed stage inthe planetary gear train according to the first and second exemplaryembodiments of the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

However, parts which are not related with the description are omittedfor clearly describing the exemplary embodiments of the presentinvention and like reference numerals refer to like or similar elementsthroughout the specification.

In the following description, dividing names of components into first,second, and the like is to divide the names because the names of thecomponents are the same as each other and an order thereof is notparticularly limited.

FIG. 1 is a schematic diagram of a planetary gear train according to thefirst exemplary embodiment of the present invention.

Referring to FIG. 1, a planetary gear train according to the firstexemplary embodiment of the present invention includes first, second,third, and fourth planetary gear sets PG1, PG2, PG3, and PG4 disposed onthe same axis, an input shaft IS, an output shaft OS, eight rotationshafts TM1 to TM8 connected to at least one of rotation elements of thefirst, second, third, and fourth planetary gear sets PG1, PG2, PG3, andPG4, seven control elements C1 to C4 and B1 to B3, and a transmissionhousing H.

As a result, torque input from the input shaft IS is changed bycooperation of the first, second, third, and fourth planetary gear setsPG1, PG2, PG3, and PG4, and the changed torque is output through theoutput shaft OS.

The simple planetary gear sets are disposed in a sequence of the first,second, third, and fourth planetary gear sets PG1, PG2, PG3, and PG4from an engine side.

The input shaft IS is an input member and power from a crankshaft of anengine is torque-converted through a torque converter to be input intothe input shaft IS.

The output shaft OS is an output member, is disposed in parallel withthe input shaft IS, and transmits driving torque to a driving wheelthrough a differential apparatus.

The first planetary gear set PG1 is a single pinion planetary gear setand includes a first sun gear S1, a first planet carrier PC1 rotatablysupporting a first pinion P1 that is externally meshed with the firstsun gear S1, and a first ring gear R1 that is internally meshed with thefirst pinion P1 respectively as first, second, and third rotationelements N1, N2, and N3.

The second planetary gear set PG2 is a single pinion planetary gear setand includes a second sun gear S2, a second planet carrier PC2 rotatablysupporting a second pinion P2 that is externally meshed with the secondsun gear S2, and a second ring gear R2 that is internally meshed withthe second pinion P2 respectively as fourth, fifth, and sixth rotationelements N4, N5, and N6.

The third planetary gear set PG3 is a single pinion planetary gear setand includes a third sun gear S3, a third planet carrier PC3 rotatablysupporting a third pinion P3 that is externally meshed with the thirdsun gear S3, and a third ring gear R3 that is internally meshed with thethird pinion P3 respectively as seventh, eighth, and ninth rotationelements N7, N8, and N9.

The fourth planetary gear set PG4 is a single pinion planetary gear setand includes a fourth sun gear S4, a fourth planet carrier PC4 rotatablysupporting a fourth pinion P4 that is externally meshed with the fourthsun gear S4, and a fourth ring gear R4 that is internally meshed withthe fourth pinion P4 respectively as tenth, eleventh, and twelfthrotation elements N10, N11, and N12.

The second rotation element N2 is directly connected to the sixthrotation element N6, the third rotation element N3 is directly connectedto the seventh rotation element N7 and the tenth rotation element N10,and the eighth rotation element N8 is directly connected to the twelfthrotation element N12 such that the first, second, third, and fourthplanetary gear sets PG1, PG2, PG3, and PG4 are operated with eightrotation shafts TM1 to TM8.

The eight rotation shafts TM1 to TM8 will be described in furtherdetail.

The first rotation shaft TM1 is connected to the first sun gear S1 andis selectively connected to the transmission housing H.

The second rotation shaft TM2 connects the first planet carrier PC1 tothe second ring gear R2.

The third rotation shaft TM3 connects the first ring gear R1, the thirdsun gear S3 and the fourth sun gear S4.

The fourth rotation shaft TM4 is connected to the second sun gear S2 andis directly connected to the input shaft IS so as to be continuouslyoperated as an input element.

The fifth rotation shaft TM5 is connected to the second planet carrierPC2 and is selectively connected respectively to the third rotationshaft TM3 and the fourth rotation shaft TM4.

The sixth rotation shaft TM6 connects the third planet carrier PC3 tothe fourth ring gear R4, is selectively connected to the first rotationshaft TM1, and is directly connected to the output shaft OS so as to beoperated as an output element.

The seventh rotation shaft TM7 is connected to the third ring gear R3and is selectively connected to the transmission housing H.

The eighth rotation shaft TM8 is connected to the fourth planet carrierPC4 and is selectively connected to the input shaft IS.

In addition, four clutches C1, C2, C3, and C4 being control elements aredisposed at connection portions between any two rotation shafts amongthe rotation shafts TM1 to TM8 or between the input shaft IS and any onerotation shaft among the rotation shafts TM1 to TM8.

In addition, three brakes B1, B2, and B3 being control elements aredisposed at connection portions between any one rotation shaft among therotation shaft TM1 to TM8 and the transmission housing H.

The seven control elements C1 to C4 and B1 to B3 will be described infurther detail.

The first clutch C1 is disposed between the first rotation shaft TM1 andthe sixth rotation shaft TM6 and selectively causes the first rotationshaft TM1 and the sixth rotation shaft TM6 to integrally rotate witheach other.

The second clutch C2 is disposed between the fourth rotation shaft TM4and the fifth rotation shaft TM5 and selectively causes the fourthrotation shaft TM4 and the fifth rotation shaft TM5 to integrally rotatewith each other.

The third clutch C3 is disposed between the input shaft IS and theeighth rotation shaft TM8 and selectively causes the input shaft IS andthe eighth rotation shaft TM8 to integrally rotate with each other.

The fourth clutch C4 is disposed between the third rotation shaft TM3and the fifth rotation shaft TM5 and selectively causes the thirdrotation shaft TM3 and the fifth rotation shaft TM5 to integrally rotatewith each other.

The first brake B1 is disposed between the fifth rotation shaft TM5 andthe transmission housing H and causes the fifth rotation shaft TM5 to beoperated as a selective fixed element.

The second brake B2 is disposed between the first rotation shaft TM1 andthe transmission housing H and causes the first rotation shaft TM1 to beoperated as a selective fixed element.

The third brake B3 is disposed between the seventh rotation shaft TM7and the transmission housing H and causes the seventh rotation shaft TM7to be operated as a selective fixed element.

The control elements including the first, second, third, and fourthclutches C1, C2, C3, and C4 and the first, second, and third brakes B1,B2, and B3 may be multi-plates friction elements of wet type that areoperated by hydraulic pressure.

FIG. 2 is a schematic diagram of a planetary gear train according to thesecond exemplary embodiment of the present invention.

Referring to FIG. 2, the second clutch C2 is disposed between the fourthrotation shaft TM4 and the fifth rotation shaft TM5 in the firstexemplary embodiment of the present invention, but the second clutch C2is disposed between the second rotation shaft TM2 and the fifth rotationshaft TM5 in the second exemplary embodiment.

The second clutch C2 in the second exemplary embodiment, the same as thesecond clutch C2 in the first exemplary embodiment, selectively connectsany two rotation elements among three rotation elements of the secondplanetary gear set PG2 so as to cause the second planetary gear set PG2to become a lock-up state.

FIG. 3 is an operation chart of control elements at each speed stage inthe planetary gear train according to the first and second exemplaryembodiments of the present invention.

As shown in FIG. 3, three control elements are operated at each speedstage in the planetary gear train according to the first exemplaryembodiment of the present invention.

The fourth clutch C4 and the second and third brakes B2 and B3 areoperated at a first forward speed stage D1. In a state that the thirdrotation shaft TM3 is connected to the fifth rotation shaft TM5 byoperation of the fourth clutch C4, torque of the input shaft IS is inputto the fourth rotation shaft TM4. In addition, the first and seventhrotation shafts TM1 and TM7 are operated as the fixed elements byoperation of the second and third brakes B2 and B3. Therefore, thetorque of the input shaft IS is shifted into the first forward speedstage, and the first forward speed stage is output through the sixthrotation shaft TM6.

The second and fourth clutches C2 and C4 and the third brake B3 areoperated at a second forward speed stage D2. In a state that the fourthrotation shaft TM4 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2 and the third rotation shaft TM3 isconnected to the fifth rotation shaft TM5 by operation of the fourthclutch C4, the torque of the input shaft IS is input to the fourthrotation shaft TM4. In addition, the seventh rotation shaft TM7 isoperated as the fixed element by operation of the third brake B3.Therefore, the torque of the input shaft IS is shifted into the secondforward speed stage, and the second forward speed stage is outputthrough the sixth rotation shaft TM6.

The second clutch C2 and the second and third brakes B2 and B3 areoperated at a third forward speed stage D3. In a state that the fourthrotation shaft TM4 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2, the torque of the input shaft IS isinput to the fourth rotation shaft TM4. In addition, the first andseventh rotation shafts TM1 and TM7 are operated as the fixed elementsby operation of the second and third brakes B2 and B3. Therefore, thetorque of the input shaft IS is shifted into the third forward speedstage, and the third forward speed stage is output through the sixthrotation shaft TM6.

The second and third clutches C2 and C3 and the third brake B3 areoperated at a fourth forward speed stage D4. In a state that the fourthrotation shaft TM4 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2 and the input shaft IS is connected tothe eighth rotation shaft TM8 by operation of the third clutch C3, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the seventh rotation shaftTM7 is operated as the fixed element by operation of the third brake B3.Therefore, the torque of the input shaft IS is shifted into the fourthforward speed stage, and the fourth forward speed stage is outputthrough the sixth rotation shaft TM6.

In another way, the third clutch C3 and the second and third brakes B2and B3 may be operated at the fourth forward speed stage D4. In a statethat the input shaft IS is connected to the eighth rotation shaft TM8 byoperation of the third clutch C3, the torque of the input shaft IS isinput to the fourth input shaft TM4 and the eighth rotation shaft TM8.In addition, the first and seventh rotation shafts TM1 and TM7 areoperated as the fixed elements by operation of the second and thirdbrakes B2 and B3. Therefore, the torque of the input shaft IS is shiftedinto the fourth forward speed stage, and the fourth forward speed stageis output through the sixth rotation shaft TM6.

The second and third clutches C2 and C3 and the second brake B2 areoperated at a fifth forward speed stage D5. In a state that the fourthrotation shaft TM4 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2 and the input shaft IS is connected tothe eighth rotation shaft TM8 by operation of the third clutch C3, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the first rotation shaft TM1is operated as the fixed element by operation of the second brake B2.Therefore, the torque of the input shaft IS is shifted into the fifthforward speed stage, and the fifth forward speed stage is output throughthe sixth rotation shaft TM6.

The second, third, and fourth clutches C2, C3, and C4 are operated at asixth forward speed stage D6. In a state that the fourth rotation shaftTM4 is connected to the fifth rotation shaft TM5 by operation of thesecond clutch C2, the input shaft IS is connected to the eighth rotationshaft TM8 by operation of the third clutch C3, and the third rotationshaft TM3 is connected to the fifth rotation shaft TM5 by operation ofthe fourth clutch C4 such that the first, second, third, and fourthplanetary gear sets PG1, PG2, PG3, and PG4 become lock-up states.Therefore, the torque of the input shaft IS is output through the sixthrotation shaft TM6 without speed change.

The third and fourth clutches C3 and C4 and the second brake B2 areoperated at a seventh forward speed stage D7. In a state that the inputshaft IS is connected to the eighth rotation shaft TM8 by operation ofthe third clutch C3 and the third rotation shaft TM3 is connected to thefifth rotation shaft TM5 by operation of the fourth clutch C4, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the first rotation shaft TM1is operated as the fixed element by operation of the second brake B2.Therefore, the torque of the input shaft IS is shifted into the seventhforward speed stage, and the seventh forward speed stage is outputthrough the sixth rotation shaft TM6.

The third and fourth clutches C3 and C4 and the first brake B1 areoperated at an eighth forward speed stage D8. In a state that the inputshaft IS is connected to the eighth rotation shaft TM8 by operation ofthe third clutch C3 and the third rotation shaft TM3 is connected to thefifth rotation shaft TM5 by operation of the fourth clutch C4, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the fifth rotation shaft TM5is operated as the fixed element by operation of the first brake B1.Therefore, the torque of the input shaft IS is shifted into the eighthforward speed stage, and the eighth forward speed stage is outputthrough the sixth rotation shaft TM6.

The third clutch C3 and the first and second brakes B1 and B2 areoperated at a ninth forward speed stage D9. In a state that the inputshaft IS is connected to the eighth rotation shaft TM8 by operation ofthe third clutch C3, the torque of the input shaft IS is input to thefourth input shaft TM4 and the eighth rotation shaft TM8. In addition,the fifth and first rotation shafts TM5 and TM1 are operated as thefixed elements by operation of the first and second brakes B1 and B2.Therefore, the torque of the input shaft IS is shifted into the ninthforward speed stage, and the ninth forward speed stage is output throughthe sixth rotation shaft TM6.

The first and third clutches C1 and C3 and the first brake B1 areoperated at a tenth forward speed stage D10. In a state that the firstrotation shaft TM1 is connected to the sixth rotation shaft TM6 byoperation of the first clutch C1 and the input shaft IS is connected tothe eighth rotation shaft TM8 by operation of the third clutch C3, thetorque of the input shaft IS is input to the fourth input shaft TM1 andthe eighth rotation shaft TM8. In addition, the fifth rotation shaft TM5is operated as the fixed element by operation of the first brake B1.Therefore, the torque of the input shaft IS is shifted into the tenthforward speed stage, and the tenth forward speed stage is output throughthe sixth rotation shaft TM6.

The first, second, and third brakes B1, B2, and B3 are operated at afirst reverse speed stage REV1. In a state that the torque of the inputshaft IS is input to the fourth input shaft TM4, the fifth, first, andseventh rotation shafts TM5, TM1, and TM7 are operated as the fixedelements by operation of the first, second, and third brakes B1, B2, andB3. Therefore, the torque of the input shaft IS is shifted into thefirst reverse speed stage, and the first reverse speed stage is outputthrough the sixth rotation shaft TM6.

The first clutch C1 and the first and third brakes B1 and B3 areoperated at a second reverse speed stage REV2. In a state that the firstrotation shaft TM1 is connected to the sixth rotation shaft TM6 byoperation of the first clutch C1, the torque of the input shaft IS isinput to the fourth rotation shaft TM4. In addition, the fifth andseventh rotation shafts TM5 and TM7 are operated as the fixed elementsby operation of the first and third brakes B1 and B3. Therefore, thetorque of the input shaft IS is shifted into the second reverse speedstage, and the second reverse speed stage is output through the sixthrotation shaft TM6.

Shifting processes of the planetary gear train according to the secondexemplary embodiment will be described in detail.

The fourth clutch C4 and the second and third brakes B2 and B3 areoperated at the first forward speed stage D1. In a state that the thirdrotation shaft TM3 is connected to the fifth rotation shaft TM5 byoperation of the fourth clutch C4, the torque of the input shaft IS isinput to the fourth rotation shaft TM4. In addition, the first andseventh rotation shafts TM1 and TM7 are operated as the fixed elementsby operation of the second and third brakes B2 and B3. Therefore, thetorque of the input shaft IS is shifted into the first forward speedstage, and the first forward speed stage is output through the sixthrotation shaft TM6.

The second and fourth clutches C2 and C4 and the third brake B3 areoperated at the second forward speed stage D2. In a state that thesecond rotation shaft TM2 is connected to the fifth rotation shaft TM5by operation of the second clutch C2 and the third rotation shaft TM3 isconnected to the fifth rotation shaft TM5 by operation of the fourthclutch C4, the torque of the input shaft IS is input to the fourthrotation shaft TM4. In addition, the seventh rotation shaft TM7 isoperated as the fixed element by operation of the third brake B3.Therefore, the torque of the input shaft IS is shifted into the secondforward speed stage, and the second forward speed stage is outputthrough the sixth rotation shaft TM6.

The second clutch C2 and the second and third brakes B2 and B3 areoperated at the third forward speed stage D3. In a state that the secondrotation shaft TM2 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2, the torque of the input shaft IS isinput to the fourth rotation shaft TM4. In addition, the first andseventh rotation shafts TM1 and TM7 are operated as the fixed elementsby operation of the second and third brakes B2 and B3. Therefore, thetorque of the input shaft IS is shifted into the third forward speedstage, and the third forward speed stage is output through the sixthrotation shaft TM6.

The second and third clutches C2 and C3 and the third brake B3 areoperated at the fourth forward speed stage D4. In a state that thesecond rotation shaft TM2 is connected to the fifth rotation shaft TM5by operation of the second clutch C2 and the input shaft IS is connectedto the eighth rotation shaft TM8 by operation of the third clutch C3,the torque of the input shaft IS is input to the fourth input shaft TM4and the eighth rotation shaft TM8. In addition, the seventh rotationshaft TM7 is operated as the fixed element by operation of the thirdbrake B3. Therefore, the torque of the input shaft IS is shifted intothe fourth forward speed stage, and the fourth forward speed stage isoutput through the sixth rotation shaft TM6.

In another way, the third clutch C3 and the second and third brakes B2and B3 may be operated at the fourth forward speed stage D4. In a statethat the input shaft IS is connected to the eighth rotation shaft TM8 byoperation of the third clutch C3, the torque of the input shaft IS isinput to the fourth input shaft TM4 and the eighth rotation shaft TM8.In addition, the first and seventh rotation shafts TM1 and TM7 areoperated as the fixed elements by operation of the second and thirdbrakes B2 and B3. Therefore, the torque of the input shaft IS is shiftedinto the fourth forward speed stage, and the fourth forward speed stageis output through the sixth rotation shaft TM6.

The second and third clutches C2 and C3 and the second brake B2 areoperated at the fifth forward speed stage D5. In a state that the secondrotation shaft TM2 is connected to the fifth rotation shaft TM5 byoperation of the second clutch C2 and the input shaft IS is connected tothe eighth rotation shaft TM8 by operation of the third clutch C3, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the first rotation shaft TM1is operated as the fixed element by operation of the second brake B2.Therefore, the torque of the input shaft IS is shifted into the fifthforward speed stage, and the fifth forward speed stage is output throughthe sixth rotation shaft TM6.

The second, third, and fourth clutches C2, C3, and C4 are operated atthe sixth forward speed stage D6. In a state that the second rotationshaft TM2 is connected to the fifth rotation shaft TM5 by operation ofthe second clutch C2, the input shaft IS is connected to the eighthrotation shaft TM8 by operation of the third clutch C3, and the thirdrotation shaft TM3 is connected to the fifth rotation shaft TM5 byoperation of the fourth clutch C4 such that the first, second, third,and fourth planetary gear sets PG1, PG2, PG3, and PG4 become lock-upstates. Therefore, the torque of the input shaft IS is output throughthe sixth rotation shaft TM6 without speed change.

The third and fourth clutches C3 and C4 and the second brake B2 areoperated at the seventh forward speed stage D7. In a state that theinput shaft IS is connected to the eighth rotation shaft TM8 byoperation of the third clutch C3 and the third rotation shaft TM3 isconnected to the fifth rotation shaft TM5 by operation of the fourthclutch C4, the torque of the input shaft IS is input to the fourth inputshaft TM4 and the eighth rotation shaft TM8. In addition, the firstrotation shaft TM1 is operated as the fixed element by operation of thesecond brake B2. Therefore, the torque of the input shaft IS is shiftedinto the seventh forward speed stage, and the seventh forward speedstage is output through the sixth rotation shaft TM6.

The third and fourth clutches C3 and C4 and the first brake B1 areoperated at the eighth forward speed stage D8. In a state that the inputshaft IS is connected to the eighth rotation shaft TM8 by operation ofthe third clutch C3 and the third rotation shaft TM3 is connected to thefifth rotation shaft TM5 by operation of the fourth clutch C4, thetorque of the input shaft IS is input to the fourth input shaft TM4 andthe eighth rotation shaft TM8. In addition, the fifth rotation shaft TM5is operated as the fixed element by operation of the first brake B1.Therefore, the torque of the input shaft IS is shifted into the eighthforward speed stage, and the eighth forward speed stage is outputthrough the sixth rotation shaft TM6.

The third clutch C3 and the first and second brakes B1 and B2 areoperated at the ninth forward speed stage D9. In a state that the inputshaft IS is connected to the eighth rotation shaft TM8 by operation ofthe third clutch C3, the torque of the input shaft IS is input to thefourth input shaft TM4 and the eighth rotation shaft TM8. In addition,the fifth and first rotation shafts TM5 and TM1 are operated as thefixed elements by operation of the first and second brakes B1 and B2.Therefore, the torque of the input shaft IS is shifted into the ninthforward speed stage, and the ninth forward speed stage is output throughthe sixth rotation shaft TM6.

The first and third clutches C1 and C3 and the first brake B1 areoperated at the tenth forward speed stage D10. In a state that the firstrotation shaft TM1 is connected to the sixth rotation shaft TM6 byoperation of the first clutch C1 and the input shaft IS is connected tothe eighth rotation shaft TM8 by operation of the third clutch C3, thetorque of the input shaft IS is input to the fourth input shaft TM1 andthe eighth rotation shaft TM8. In addition, the fifth rotation shaft TM5is operated as the fixed element by operation of the first brake B1.Therefore, the torque of the input shaft IS is shifted into the tenthforward speed stage, and the tenth forward speed stage is output throughthe sixth rotation shaft TM6.

The first, second, and third brakes B1, B2, and B3 are operated at thefirst reverse speed stage REV1. In a state that the torque of the inputshaft IS is input to the fourth input shaft TM4, the fifth, first, andseventh rotation shafts TM5, TM1, and TM7 are operated as the fixedelements by operation of the first, second, and third brakes B1, B2, andB3. Therefore, the torque of the input shaft IS is shifted into thefirst reverse speed stage, and the first reverse speed stage is outputthrough the sixth rotation shaft TM6.

The first clutch C1 and the first and third brakes B1 and B3 areoperated at the second reverse speed stage REV2. In a state that thefirst rotation shaft TM1 is connected to the sixth rotation shaft TM6 byoperation of the first clutch C1, the torque of the input shaft IS isinput to the fourth rotation shaft TM4. In addition, the fifth andseventh rotation shafts TM5 and TM7 are operated as the fixed elementsby operation of the first and third brakes B1 and B3. Therefore, thetorque of the input shaft IS is shifted into the second reverse speedstage, and the second reverse speed stage is output through the sixthrotation shaft TM6.

The planetary gear train according to the exemplary embodiments of thepresent invention may achieve ten forward speed stages and two reversespeed stages by control of four planetary gear sets PG1, PG2, PG3, andPG4, four clutches C1, C2, C3, and C4, and three brakes B1, B2, and B3.

In addition, since linearity of step ratios is secured, drivability suchas acceleration before and after shift, rhythmical engine speed, and soon may be improved.

In addition, since gear ratio span greater than 9.0 is secured, drivingefficiency of the engine may be maximized.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner” and “outer” are used todescribe features of the exemplary embodiments with reference to thepositions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings as well as various alternatives and modifications thereof. Itis intended that the scope of the invention be defined by the Claimsappended hereto and their equivalents.

What is claimed is:
 1. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft receiving torqueof an engine; an output shaft outputting changed torque; a firstplanetary gear set including a first rotation element, a second rotationelement, and a third rotation element; a second planetary gear setincluding a fourth rotation element, a fifth rotation element, and asixth rotation element; a third planetary gear set including a seventhrotation element, an eighth rotation element, and a ninth rotationelement; and a fourth planetary gear set including a tenth rotationelement, an eleventh rotation element, and a twelfth rotation element,wherein the input shaft is directly connected to the fourth rotationelement and is selectively connected to the eleventh rotation element,the output shaft is directly connected to the twelfth rotation element,the twelfth rotation element is directly connected to the eighthrotation element, the third rotation element is directly connected tothe seventh and tenth rotation elements, the second rotation element isdirectly connected to the sixth rotation element, the first rotationelement is selectively connected to the eighth rotation element, thefourth rotation element is selectively connected to the fifth rotationelement, the third rotation element is selectively connected to thefifth rotation element, the fifth rotation element is selectivelyconnected to the transmission housing, the first rotation element isselectively connected to the transmission housing, and the ninthrotation element is selectively connected to the transmission housing.2. The planetary gear train of claim 1, wherein the first rotationelement, the second rotation element, and the third rotation element ofthe first planetary gear set are a first sun gear, a first planetcarrier, and a first ring gear, the fourth rotation element, the fifthrotation element, and the sixth rotation element of the second planetarygear set are a second sun gear, a second planet carrier, and a secondring gear, the seventh rotation element, the eighth rotation element,and the ninth rotation element of the third planetary gear set are athird sun gear, a third planet carrier, and a third ring gear, and thetenth rotation element, the eleventh rotation element, and the twelfthrotation element of the fourth planetary gear set are a fourth sun gear,a fourth planet carrier, and a fourth ring gear.
 3. The planetary geartrain of claim 2, wherein each of the first, second, third, and fourthplanetary gear sets is a single pinion planetary gear set.
 4. Theplanetary gear train of claim 1, further comprising: a first clutchselectively connecting the first rotation element to the eighth rotationelement; a second clutch selectively connecting the fourth rotationelement to the fifth rotation element; a third clutch selectivelyconnecting the input shaft to the eleventh rotation element; a fourthclutch selectively connecting the third rotation element to the fifthrotation element; a first brake selectively connecting the fifthrotation element to the transmission housing; a second brake selectivelyconnecting the first rotation element to the transmission housing; and athird brake selectively connecting the ninth rotation element to thetransmission housing.
 5. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft receiving torqueof an engine; an output shaft outputting changed torque; a firstplanetary gear set including a first rotation element, a second rotationelement, and a third rotation element; a second planetary gear setincluding a fourth rotation element, a fifth rotation element, and asixth rotation element; a third planetary gear set including a seventhrotation element, an eighth rotation element, and a ninth rotationelement; and a fourth planetary gear set including a tenth rotationelement, an eleventh rotation element, and a twelfth rotation element,wherein the input shaft is directly connected to the fourth rotationelement and is selectively connected to the eleventh rotation element,the output shaft is directly connected to the twelfth rotation element,the twelfth rotation element is directly connected to the eighthrotation element, the third rotation element is directly connected tothe seventh and tenth rotation elements, the second rotation element isdirectly connected to the sixth rotation element, the first rotationelement is selectively connected to the eighth rotation element, thefifth rotation element is selectively connected to the sixth rotationelement, the third rotation element is selectively connected to thefifth rotation element, the fifth rotation element is selectivelyconnected to the transmission housing, the first rotation element isselectively connected to the transmission housing, and the ninthrotation element is selectively connected to the transmission housing.6. The planetary gear train of claim 5, wherein the first rotationelement, the second rotation element, and the third rotation element ofthe first planetary gear set are a first sun gear, a first planetcarrier, and a first ring gear, the fourth rotation element, the fifthrotation element, and the sixth rotation element of the second planetarygear set are a second sun gear, a second planet carrier, and a secondring gear, the seventh rotation element, the eighth rotation element,and the ninth rotation element of the third planetary gear set are athird sun gear, a third planet carrier, and a third ring gear, and thetenth rotation element, the eleventh rotation element, and the twelfthrotation element of the fourth planetary gear set are a fourth sun gear,a fourth planet carrier, and a fourth ring gear.
 7. The planetary geartrain of claim 6, wherein each of the first, second, third, and fourthplanetary gear sets is a single pinion planetary gear set.
 8. Theplanetary gear train of claim 1, further comprising: a first clutchselectively connecting the first rotation element to the eighth rotationelement; a second clutch selectively connecting the fifth rotationelement to the sixth rotation element; a third clutch selectivelyconnecting the input shaft to the eleventh rotation element; a fourthclutch selectively connecting the third rotation element to the fifthrotation element; a first brake selectively connecting the fifthrotation element to the transmission housing; a second brake selectivelyconnecting the first rotation element to the transmission housing; and athird brake selectively connecting the ninth rotation element to thetransmission housing.
 9. A planetary gear train of an automatictransmission for a vehicle, comprising: an input shaft receiving torqueof an engine; an output shaft outputting changed torque; a firstplanetary gear set including a first rotation element, a second rotationelement, and a third rotation element; a second planetary gear setincluding a fourth rotation element, a fifth rotation element, and asixth rotation element; a third planetary gear set including a seventhrotation element, an eighth rotation element, and a ninth rotationelement; a fourth planetary gear set including a tenth rotation element,an eleventh rotation element, and a twelfth rotation element; a firstrotation shaft connected to the first rotation element and selectivelyconnected to a transmission housing; a second rotation shaft connectingthe second rotation element to the sixth rotation element; a thirdrotation shaft connecting the third rotation element to the seventh andtenth rotation elements; a fourth rotation shaft connected to the fourthrotation element and directly connected to the input shaft; a fifthrotation shaft connected to the fifth rotation element, selectivelyconnected to the transmission housing, and selectively connected to thethird rotation shaft; a sixth rotation shaft connecting the eighthrotation element to the twelfth rotation element, selectively connectedto the first rotation shaft, and directly connected to the output shaft;a seventh rotation shaft connected to the ninth rotation element andselectively connected to the transmission housing; and an eighthrotation shaft connected to the eleventh rotation element andselectively connected to the input shaft, wherein the second planetarygear set is selectively locked-up by selectively connecting two rotationelements among three rotation elements of the second planetary gear set.10. The planetary gear train of claim 9, wherein the first planetarygear set is a single pinion planetary gear set and includes a first sungear as the first rotation element, a first planet carrier as the secondrotation element, and a first ring gear as the third rotation element,the second planetary gear set is a single pinion planetary gear set andincludes a second sun gear as the fourth rotation element, a secondplanet carrier as the fifth rotation element, and a second ring gear asthe sixth rotation element, the third planetary gear set is a singlepinion planetary gear set and includes a third sun gear as the seventhrotation element, a third planet carrier as the eighth rotation element,and a third ring gear as the ninth rotation element, and the fourthplanetary gear set is a single pinion planetary gear set and includes afourth sun gear as the tenth rotation element, a fourth planet carrieras the eleventh rotation element, and a fourth ring gear as the twelfthrotation element.
 11. The planetary gear train of claim 9, wherein thesecond planetary gear set is locked-up by connection of the fourthrotation element and the fifth rotation element.
 12. The planetary geartrain of claim 11, further comprising: a first clutch selectivelyconnecting the first rotation shaft to the sixth rotation shaft; asecond clutch selectively connecting the fourth rotation shaft to thefifth rotation shaft; a third clutch selectively connecting the inputshaft to the eighth rotation shaft; a fourth clutch selectivelyconnecting the third rotation shaft to the fifth rotation shaft; a firstbrake selectively connecting the fifth rotation shaft to thetransmission housing; a second brake selectively connecting the firstrotation shaft to the transmission housing; and a third brakeselectively connecting the seventh rotation shaft to the transmissionhousing.
 13. The planetary gear train of claim 9, wherein the secondplanetary gear set is locked-up by connection of the fifth rotationelement and the sixth rotation element.
 14. The planetary gear train ofclaim 13, further comprising: a first clutch selectively connecting thefirst rotation shaft to the sixth rotation shaft; a second clutchselectively connecting the second rotation shaft to the fifth rotationshaft; a third clutch selectively connecting the input shaft to theeighth rotation shaft; a fourth clutch selectively connecting the thirdrotation shaft to the fifth rotation shaft; a first brake selectivelyconnecting the fifth rotation shaft to the transmission housing; asecond brake selectively connecting the first rotation shaft to thetransmission housing; and a third brake selectively connecting theseventh rotation shaft to the transmission housing.